Catalyst for steam reforming of hydrocarbons

ABSTRACT

An improved catalyst is described which comprises a normally cylindrical refractory support having gas passages communicating from end to end and oriented parallel to its axis and having gas passages in the shape of segments of circles (pie-shaped), square, hexagonal, circular, oval or sinusoidal. The exterior and interior surfaces are coated with catalytic compositions. The length of the refractory support is significantly less than the diameter. Further, there is a definite ratio of height to effective internal diameter (H:ID) of each of the gas passages. These catalysts are especially effective for endothermal reactions because both the internal and external surfaces of the support are coated with catalysts and are more efficiently heated. This is especially true for the internal surfaces of the support (i.e., the walls of the axially oriented gas passages) which heretofore have been shielded from the infra-red rays radiating from the tubes of the catalytic reactor. Thus, heat transfer to the catalyst surface is more effective in maintaining the interior surface at the desired elevated reaction temperature. The structures are especially effective for the steam-hydrocarbon reforming reaction, particularly when the hydrocarbon is in the boiling range of naphtha or below.

CROSS REFERENCE TO RELATED APPLICATION

This application is a Continuation-In-Part of our Co-Pending applicationentitled CATALYST AND PROCESS FOR STEAM REFORMING OF HYDROCARBONS, Ser.No. 024,005, Filed: Mar. 26, 1979, now U.S. Pat. No. 4,233,187, whichwas a Continuation-In-Part of our Co-Pending application entitled STEAMHYDROCARBON REFORMING PROCESS, Ser. No. 817,160, Filed: July 20, 1977,now abandoned, and of our co-pending application Ser. No. 708,941,Filed: July 27, 1976, now abandoned.

FIELD OF THE INVENTION

This invention relates to an improved geometric configuration for acatalyst support which is especially effective and efficient whenemployed for endothermal reactions. It is more particularly applicable,especially when coated with nickel promoted with the oxides of iron andmanganese, such as those described in co-pending application Ser. No.638,505, filed Dec. 8, 1975, now U.S. Pat. No. 4,233,179, and in U.S.Pat. No. 4,207,211. When these specific structures and catalystcompositions are utilized in steam-hydrocarbon reforming operations, thetroublesome problem of the deposition of carbonaceous matter on thecatalyst is significantly reduced.

BACKGROUND OF THE INVENTION

There are several types of endothermal reactions that are extensivelyutilized on a commercial basis. This invention relates to thesteam-hydrocarbon reforming reaction for the production of Hydrogen,Carbon Monoxide and synthesis gas. The steam hydrocarbon reformingprocess is conducted in externally fired multitubular reactors usingfixed catalyst beds. As less endothermal reaction occurs the temperatureof the reaction is increased. Finally, the tube temperatures increaseand may approach that of the furnace itself. Such temperatures, ifreached, are extremely damaging to the metal tubes and costlyreplacement of the expensive alloy tubes may be required. Even if thetube temperatures do not reach this severity, the operation must be shutdown with increasing frequency, the catalyst must be changed andconsiderable operating time and production is thus lost.

However, it has been discovered that if heat exchange can be improvedfrom the furnace through the tubewall and to the catalyst within thetube, the problem of loss of activity can be minimized. This isespecially true if the catalyst is on specific support shapes and if thecatalyst is of the type disclosed in co-pending application Ser. No.638,505, filed: Dec. 8, 1975, and in U.S. Pat. No. 4,207,211 dated June10, 1978. The most logical explanation for the increased efficiency ofthis structure is that because of the low length to diameter ratio, alarger fraction of the surface of the interior walls of the support'saxially aligned gas passages receive almost direct radiation from thetubewalls. The direct radiation (temperature in the 1200° F. to 2000° F.range) is at almost vertical incidence to the interior wall surface andthus the direct absorption of radiation is enhanced. This assuresefficient heat exchange from the furnace hot gases and a low delta Tbetween this gas temperature and the catalyst temperature. This makesfor the good utilization of the heat in the furnace and a high energyefficiency.

Pressure drop through the steam-hydrocarbon reformer tubes hashistorically been a severe problem and one which in the past has been.Iadd.a .Iaddend.frequent cause of catalyst failure. The unique catalyststructure of this invention overcomes much of this problem by providingmore passages for the gas flowing through the tubes. These addedchannels or passages facilitate the gas transport through the tubes andthus decrease pressure drop.

SUMMARY OF THE INVENTION

This invention provides a new catalyst particularly useful forendothermal chemical reactions. More particularly, it encompasses acatalyst type having great importance to the steam-hydrocarbon reformingreaction. This reaction produces reactant gases for such importantreactions as alcohol and ammonia synthesis. The hydrogen required forpetrochemical and hydrogenation reactions is also prepared in thismanner. The improved catalyst has two very important features, onegeometric and the second catalytic composition. The geometric featureassures a multiplicity of gas passages or gas channels through thestructure of such a length to diameter ratio, that most of the interiorsurface walls of the gas passages can be radiated directly from the hotwalls of the reactor tubes. These surfaces, directly radiated, arecoated with specific catalyst constituents comprising nickel or cobaltin concentrations of from about 6 to 30% by weight expressed as themetal oxide and which may be promoted with manganese, iron or bariumoxides in predetermined and specified proportions. This combination ofphysical and chemical characteristics produces a unique and unusuallyefficient and longlived catalyst. A further advantage of these catalystsis that they actually benefit from being installed into the convertertubes in a random rather than in an oriented or ordered manner. By sodoing, the cost of charging is sharply reduced and the problem ofbypassing at the tube walls is essentially eliminated.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the drawings,

FIG. 1 is an end view of one of the preferred embodiments of thisinvention, illustrating the structure of the catalyst and particularlyone way in which the multichannel concept can be designed. The outsideshape is that of a cylinder.

FIG. 2 illustrates in more detail the configuration of the gas passages,their relative positions, and the location of the catalytic componentson the surfaces.

FIG. 3 illustrates in even more detail the presence of macropores whichfunction as cells for catalyst anchoring and functioning.

FIG. 4 is an end view of the honeycomb catalyst having square channelsas an alternate to the sinusoidal type illustrated in FIG. 1.

FIG. 5 is an end view also of the square sectioned cells but with largerwall thickness and opening size.

FIG. 6 is a diagrammatic representation of heat radiating rays(infra-red) striking the interior walls of the gas channels.

FIG. 7 is an end view of a catalyst structure in the form of a spokedwheel and is one of the most preferred forms of this invention. Thisspoked wheel fabricated of refractory material has a peripheral rim anda centrally located "hub" with seven radiating webs or spokes extendingfrom the hub to the solid peripheral rim defining pie shaped gaspassages.

FIG. 8 is similar to FIG. 7 except that the circle is divided into five(5) equal segments instead of seven (7) as in FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The basic purpose of the invention is to improve the economics of thesynthesis gas operation by utilizing a catalyst having structural andchemical characteristics which .[.increases.]. .Iadd.increase.Iaddend.catalytic activity catalyst life and which .[.tends.]..Iadd.tend .Iaddend.to reduce carbon deposition in the reactor tubes.The formation of carbon is especially severe when heavy hydrocarbons areprocessed (naptha or lighter) and when these hydrocarbons are exposed toa temperature below the optimum.

The structure of the catalyst 5 is such that radiation to all catalyticsurfaces is so efficient that a high temperature is maintained even inthe interior passages of the structure.

A part of the explanation given above can be better visualized byreferring to FIGS. 3 and 6. FIG. 3 illustrates the refractory structure6 as having macropores 8. The gas passages or gas channels 9 are definedby corrugations 10 interposed between horizontal layer 13. The catalyticconstituent 12 should be thought of as a mossy or powdery coatingadhering to all surfaces. Some pores, as for example 7, are of a largersize pore i.e., somewhat bigger than the macropores 8. Thisrepresentation of the typical supported catalyst surface is generallyaccepted as being the profile of catalysts supported on "low surfacearea" supports. Such supports having a surface area as measured by BETof from 0.5-55 m² /gm.

The role of FIG. 6 is essentially to make evident in a simple diagramthe basic accomplishment of the invention of achieving radiant energytransfer from the hot reactor tubewalls to the catalytic surfaces andespecially to the internal walls of the gas passages in .Iadd.the.Iaddend.supported catalyst of this invention.

FIGS. 7 and 8 are end views of catalysts in the form of spoked wheelsand are the preferred forms of this invention. This form has a central"axle" or "hub" 15 with radiating webs or spokes 16 extending from thehub 15 to the solid rim 14.

FIG. 6 diagrammatically illustrates a theoretical postulate as to theoperation of the catalyst of this invention under process conditions.The explanation involves certain assumptions. One of these assumptionsinvolves the comparison of gas molecules with infra-red rays. Thepurpose of the explanation is to determine the effectiveness of theinner surface of the holes as a catalytic contact surface, i.e. thesurface area provided by the inner walls of the gas passages 9 ascontrasted with the effectiveness of the exterior surface encounteredwith solid cylinders, spheres and the like. Following this analogy, itis assumed that the interior surface of the holes would receive lessradiation from the skin of the furnace tube than the exterior surface ofthe cylinder, i.e. that the middle of the gas channel would be lessradiated than would be the area surrounding the gas .[.channels.]..Iadd.channel's .Iaddend.entrance. This lack of heat radiation wasthought to be proportional to the length of the gas channel (height ofthe tablet). Further, since the reaction is endothermic and since heatmust be supplied to the reactor by externally fired burners impinging onthe skin of the tubes containing the catalyst, it is hypothesized thatnot only is the channel less radiated in the middle, but that due to theheat absorbing reaction in the middle of the channel, .[.sheilded.]..Iadd.shielded .Iaddend.by the ceramic catalyst wall from the externalsource of heat, (i.e. the radiating skin of the tubes) that it is alsocooler in the middle portion of the gas channel. The postulate is, then,that catalytic activity and heat transfer of the interior surface of thewalls of the gas channels are inversely proportional to the height ofthe tablet (length of the channel) and directly proportional to thediameter of the hole (width of the channel) and that therefore there isa relationship between the effectiveness of the catalyst pellet and theratio of pellet height versus effective hole diameter (H:ID).

FIG. 6 was designed to demonstrate this and involves two parallel linesdrawn to simulate the walls of the gas channel in the catalyst support.The sum of the two angles which could strike each point over the lengthof these lines is integrated as is shown in FIG. 6.

Now integrating Σ(θ1+θ2)dx from x=0 to x=1

Where RA=H:ID (ratio of Height to Diameter of the Hole)

d=the derivative of the length

x=the length

It is found that as RA approaches 0, Σ approaches 2 pi.

The symbol F1, as used herein, indicates the effectiveness of thecatalytic surface both for catalytic activity and for heat transfer.

Therefore, F1=0.63662×ATAN

    [1/(RA-2.5)]+0.31831/.Iadd.(.Iaddend.RA-2.5.Iadd.).Iaddend.×ALOG[1+(RA-2.5).sup.2 ].

Where 0.63662 is a constant derived from the integration.

Where 0.31831 is a constant derived from the integration.

Where 2.5=the ratio of H:D of a 5/8×1/4" ring.

This factor of 2.5 takes into consideration the turbulent whirlpooleffect of gas molecules at the entrance of the hole opening (ascontrasted with the straight line path of infra-red rays) and is inagreement with commercial experience to the effect that 5/8"×5/8"×1/4"rings exhibit an activity indicating that both the interior and exteriorsurfaces of the rings of this dimension are fully effective. Therefore,since the inner walls of the 5/8" ring having 1/4" diameter opening areapparently fully effective, this value is subtracted from the RA factorfor the computation. When the various RA factors are from 1-10, that is(height to effective hole diameter ratios of 1:1 to 10:1) the followingF1 (catalytic effectiveness) values are obtained.

                  TABLE I                                                         ______________________________________                                                RA   F1                                                               ______________________________________                                                10   .256                                                                     5    .494                                                                     4    .624                                                                     3    .847                                                                     2    1.000                                                                    1    1.000                                                            ______________________________________                                    

It is clear.Iadd., .Iaddend.then.Iadd., .Iaddend.from the theoreticalvalues that a height to effective hole diameter (H:ID) ratio of 4:1 isequivalent to a +60% catalytic effectiveness. This value increases up to100% as the ratio is lowered. Conversely.Iadd., .Iaddend.at values forH:ID ratios greater than 4.Iadd., .Iaddend.the catalytic effectivenessdecreases from around 50% down to around 25%. The structure of the art(length equal to diameter) does not accomplish this because radiation isshielded from at least half of the interior catalytic surface.

The foregoing tends to explain how the purpose of this invention isaccomplished, i.e., by a specific catalyst composition and a specificcatalyst structure which provides much more catalytic surface thanstructures of the art and, because of the length to effective holediameter (or width) considerations, assuring that heat is efficientlyradiated to all of these surfaces maintaining the surfaces (catalystentity) at a sufficiently high temperature to assure a high reactionrate for steam-hydrocarbon reforming and other endothermal chemicalreactions.

The structures can be fabricated preferably from alpha alumina but othercompositions can be employed and may be superior for certainapplications. Examples of effective compositions other than alphaalumina include: metal aluminate spinel (as for example magnesiumaluminate as represented by the formula R Q₂ O₄ in which R representsone or more divalent metals (such as magnesium or zinc) and Q one ormore trivalent metals, as for example, manganese, cobalt or chromium);alpha alumina containing calcium oxide, (or calcium aluminate cement);alpha alumina containing alkali salts such as K₂ O, Na₂ O, or Cs₂ O;zirconium oxide; titanium oxide; magnesium oxide; thoria and ceria. Rareearth oxides can be used individually or as rare earth oxide mixtures asstabilizer mixtures for the foregoing. As has previously beendemonstrated in our pending application Ser. No. 24,005, filed: Mar. 26,1979, now U.S. Pat. No. 4,233,187, and its parent applications,Cordierite (Mg₂ Al₄ Si₅ O₁₈)(magnesium alumino silicate) does not havesufficient activity for the steam hydrocarbon reforming reaction. Therequirement is that the products have a surface area as measured by theBET procedure in the range of 0.5 to 55 m² /gm; by physically strong;chemically and catalytically compatible with the reaction and reactionenvironment; chemically inert with the catalytic constituents underreaction conditions; and adaptable to at least one of many preparativeand fabricating procedures. Originally spinel designated a mineral i.e.,the double oxide of magnesium and aluminum viz. Mg Al₂ O₄. As pointedout in U.S. Pat. No. 3,436,358, the double oxide can now besynthetically produced. Spinel is an extremely hard and physically avery resistant material having a hardness in the Moh's scale of about 8.It is therefore physically strong and resistant to spalling anddisintegration. Further, it is resistant to reduction and reaction withthe catalytic constituents under reaction conditions. As previouslymentioned, while magnesium aluminate is the preferred carrier material,other divalent metals, as for example zinc, can replace all or part ofthe magnesium constituent and trivalent metals such as manganese.[.coablt.]. .Iadd.cobalt .Iaddend.or chromium can represent thetrivalent metals in the formula. We therefore designate these materialsas metal aluminate spinels.

We have found, however, that the metal aluminate spinels are superiorsupports for the catalytic materials of this invention and are resistantto carbon formation, to physical disintegration, and to thermal shock.

The catalytic metals and metal oxides for this type catalyst are wellknown. Nickel and cobalt which may be incorporated by known methods ontothe carrier in a concentration of from about 6 to 30% by weight(expressed as the oxides) are preferred. These catalytic agents may befurther promoted by known promoters such as alkali metal oxides, or ironoxide and manganese oxide present in specific proportions.

When the alumina is idenfified as alpha, it is understood that this isdetermined by accepted X-ray procedures which fail to identify as muchas 5% of other phases which may also be present. This, however, isaccepted in crystallographic terminology, to indicate essentially all ifnot 100% alpha when a species is so identified. As given above in theranges, the surface area should not significantly exceed 55 m² /gm.

The preferred catalytic constituents employed are described inapplication Ser. No. 638,505, filed Dec. 8, 1975, now U.S. Pat. No.4,233,179, and in U.S. Pat. No. 4,207,211. This disclosure teaches thatthe preferred composition contains nickel, manganese, iron, andoptionally barium all as oxides. The barium oxide is beneficially addedlast. The basic principle for the impregnation is that either the ironor manganese can be added first but the nickel and the other promotermust be added subsequent to the first coating. The further requirementfor a satisfactory catalyst is for the iron to manganese ratio not toexceed the value of two. The structures can be coated by immersion,spray coating or dipping .Iadd.a .Iaddend.perforated basket containingthe support structures into an impregnating solution.

The foregoing is offered as one explanation for the improved performanceof the invention herein disclosed. However, an entirely separateexplanation and analysis is presented also as follows:

The art has not recognized that geometric surface area provided by theinterior walls of catalysts having multiple gas passages (multiholecatalysts) does not contribute fully to catalytic activity inendothermic reactions. Our research has shown that while the exteriorsurface of the catalyst is available as sites for catalytic activity,that only the effective surface area provided by the interior gaspassage walls contributes to catalytic activity. As a rule, we havefound that with multiholed catalysts in endothermic reactions, that thegeometric area of the exterior surface is directly proportional tocatalytic activity and that catalyst efficiency is inverselyproportional to the height (or length) of the catalyst pellet.

Furthermore, the effective surface area of the interior gas channelwalls of multihole catalysts bears a relationship of table height (orlength) to gas passage width or diameter (H:ID). The effective diameteris defined as the width of the opening of the gas passageway, when thearea of said opening is expressed as .Iadd.a .Iaddend○ This expressionis necessitated since the gas passage openings may be circular, square,rectangular, trapezoidal, triangular, sinusoidal, etc. The exactconfiguration of the gas passage is immaterial. What does matter is therelationship of the height of the catalyst pellet to the effectiveinternal diameter of the gas passage. In making these determinations,the following constants, utilized in the equations were derived from thefollowing references.

Campbell, John M., and Huntington, R. L., "Heat Transfer and PressureDrop in Fixed Beds of Spiral and Cylindrical Solids." Petroleum Refiner,Vol. 30, Number 12 (1951) pp. 127-133.

Leva, Max, "Pressure Drop Through Packed Tubes, Part I, A generalCorrelation" Chemical Engineering Progress, Vol. 43 (1947) pp. 549-54.

Leva, Max and Grummer, Milton, IBID. 1947) 633-648.

Leva, Max, IBID. pp. 713-718.

The values of these constants are:

    a=0.373

    b=1.848

    c=0.1393

Let:

FH=Fraction of particle taken up by hole(s)

FHS=FH

DT=Tube I.D. in which the particles are to be packed

A'=Area of particles with no hole(s)

F'=Fraction voids of particle with no hole(s) ##EQU1## A=Area ofparticles with hole(s) V=Volume of particle with hole(s)

F=Actual fraction voids ##EQU2##

ACTIVITY COEFFICIENT FACTOR=ACF ##EQU3## PRESSURE FACTOR=PF ##EQU4##

The Relative Activity Coefficient Factor is obtained by dividing thevalue of the ACF for the .[.standard.]. .Iadd.sample .Iaddend.by the ACFvalue of the .[.sample.]..Iadd.standard.Iaddend.. Thus,ACF.[.®.]..Iadd.^(R) .Iaddend.for the standard becomes one, whereascatalysts having an ACF greater than the standard have a value in excessof one. The ability of the catalyst to promote heat transfer into thereacting gas is essentially proportional to the activity factor. TheRelative Activity Coefficient Factor .[.(ACF®).]..Iadd.ACF^(R).Iaddend., and the Relative Pressure Factor .[.(PF®).]. .Iadd.PF^(R).Iaddend.for each of the carriers illustrated in FIGS. 4, 5, 6 and 7 areas follows:

                                      TABLE II                                    __________________________________________________________________________    (Based on a 2.9 inch ID tube)                                                                           RATIO                                                       ACF.sup.R                                                                            PF.sup.R                                                                              PF.sup.R .]..[.ACF.sup.R                                                          ##STR1##                                                                           (in.)Diameter                                                                      (in.)Height                                                                       (in.)ID                                                                          HolesNo. of                       __________________________________________________________________________    Standard                                                                             1      1                .625 .375                                                                              .25                                                                               1                                 Honeycomb                                                                            2.48   .[..47.].                                                                         .Iadd..94.Iaddend.                                                               .[.5.28.].                                                                         .Iadd.2.63.Iaddend.                                                                .785 .797                                                                              .076                                                                             46                                 FIG. 4                                                                        Honeycomb                                                                            .[..206.].                                                                        .Iadd.2.16.Iaddend.                                                              .[..39.].                                                                         .Iadd..70.Iaddend.                                                               .[.5.62.].                                                                         .Iadd.3.09.Iaddend.                                                                .625 .250                                                                              .135                                                                             11                                 FIG. 5                                                                        __________________________________________________________________________

It should be noted that the honeycomb of FIG. 4 produced the largestrelative ACF.[.®.]..Iadd.^(R) .Iaddend.and the largest value of theratio of ACF.[.®.]..Iadd.^(R) .Iaddend.:PF.[.®.]..Iadd.^(R) .Iaddend..

The conditions for the steam-hydrocarbon reforming reaction are wellknown and vary from temperatures of 800° F. to 1800° F. and pressures of0 to 600 psig. As the pressure is increased, the severity of theconditions increase. Further, as the temperature increases, the severityof conditions to which the catalyst is subjected is increased.

It is standard practice, in the field, to increase the skin temperatureof the catalytic reactor tubes to maintain a given rate of synthesis gasproduction. Therefore, the skin temperature of the tube at a particularlocalized point in the reactor can become critical and the lower thetemperature that can be maintained at a specific catalytic activity, thelower the fuel consumption in the reformer and the less stress placed onthe catalytic reformer tubes. The steam-to-carbon ratio varies incommercial practice .[.of.]. from 1.5:1 to 8:1. It is well known, ofcourse, that as the length of the hydrocarbon feedstock chain isincreased, the steam to carbon ratio must be increased to prevent andminimize carbon deposition. Neverless, the lower the steam-to-carbonratio that can be maintained, the lower the steam requirement and as aresult the lower the fuel requirement for the process.

SUPPORT PREPARATION

The following ingredients were carefully weighed out:

96.5 parts by weight of alpha alumina as a powder passing 100% through a325 mesh screen.

10.5 parts by weight of Boehmite alumina (alpha alumina monohydrate).

50.0 parts by weight of recycle material (oversize from a previousbatch).

Add all of the three ingredients above to a mix muller and start themixer operating and grind or mill for about 10 minutes.

2. Prepare a nitric acid solution as follows:

25 parts by weight of distilled or demineralized water.

7.5 parts by weight of 61% nitric acid.

3. Add the solution of paragraph 2 to the milled powder of paragraph 1.

4. Mix mull the resultant moist paste for an additional 30 minutes, thenadd 6.2 parts by weight of distilled or demineralized water to the mixerand then mix mull for an additional period.

5. Transfer all the mixed product obtained to a continuous drier.

6. The dried granular material is next pulverized.

7. Blend the granular pieces with:

2.95 parts by weight of a lubricant.

8. Screen the product.

9. The screened product is now formed into cylinders, as shown inattached FIG. 7, 0.648 inches in diameter 0.293 inches high and withribs 0.060 inches thick.

10. The supports from 9 are "program fired" at a temperature starting at2200° F. and eventually reaching 2700° F. stepwise over a 4 hour periodin an oxidizing atmosphere. The seven spoked wheel, correspondinggenerally to the catalyst shown in Example 7, was utilized throughout.The catalyst support had the following dimension .Iadd.3:3.Iaddend..

                  TABLE III                                                       ______________________________________                                                                 EQUIV-                                                                        ALENT                                                DIA-                     HOLE                                                 METER  INNER    SPOKE    DIA-   RA-                                           IN     DIMEN-   THICK-   METER  TIO   HEIGHT IN                               INCHES SION     NESS     ID     H:ID  INCHES H                                ______________________________________                                        .648   .498     .060     .1372  2.14  .293                                                                          Example 1A                              .648   .498     .060     .1372  4.72  .648                                                                          Example 1B                              ______________________________________                                    

The equivalent hole diameter, ID of each of the pie shaped gas passages9, expressed as a circle was 0.1372" and was identical for both samples.The only difference, therefore, was the height or the length of thetablet and the ratio of H:ID. The longer of the samples (Example 1B) hada ratio of H:ID of 4.72:1 whereas the shorter of the samples was withinthe claimed range of 2.14:1.

EXAMPLE 1A

A series of the .[.catalysts.]. .Iadd.catalyst .Iaddend.supportsprepared according to the following prepration were immersed into anickel nitrate solution and dried and calcined to convert the nickelnitrate to the oxide. The calcined material was then redipped in thenickel nitrate solution and this procedure was continued until a nickelconcentration, expressed as the oxide.Iadd., .Iaddend.of 19.0% wasobtained on the catalyst support. As previously indicated, thisnickel.[.,.]. is present in the macropores 7 and 8 both on the insideand outer surfaces of the catalyst, i.e. in the gas channels 9 as wellas the exterior walls of the cylinder 6.

This catalyst had the characteristics as shown in Table IV attached.

EXAMPLE 1B

This catalyst was prepared in the identical method as that of example 1Aexcept that the length of this catalyst support was 0.648" rather than0.293". The nickel was incorporated by repeated immersion into a nickelnitrate solution, followed by multiple dryings and calcinations. Thefinal nickel concentration contained in the finished catalyst was 19.0%,expressed as the oxide.

EXAMPLE 2

This preparation has as its composition calcium aluminate as a binderand is one of the preferred compositions. The procedure for preparationis as follows:

1. The following ingredients are carefully weighed out:

A. 33.9 parts by weight of calcium aluminate cement (the cement is inturn comprised of 6.1 parts CaO and 27.8 parts (Al₂ O₃).

B. 66.1 parts of Al₂ O₃ derived from Al (OH)₃, alumina hydrate which isapproximately 61% Al₂ O₃.

C. 25.0 parts by weight of recycle material.

Add all of the three ingredients to a mix muller and mix the materialfor about 10 minutes.

2. .[.weight.]. .Iadd.weigh .Iaddend.out 25 parts by weight of distilledwater.

3. Perform operations as set forth in paragraphs 3 through 6 of Example1.

4. Blend the product of paragraph 6 with 3 parts of powdered graphite.

5. Operations as described in paragraphs 8, 9 and 10 are performed ascalled for in "Support Preparation." The calcined 7 spoked cylinders areimpregnated by immersing a quantity into a nickel nitrate solution. Theimmersed supports are dried and calcined. This procedure is repeateduntil the nickel oxide concentration of the finished catalyst is in therange of 19%. The calcination temperature is in the range of 650°F.-750° F. The finished catalyst contained:

    ______________________________________                                        NiO       Calcium Aluminate                                                                           Alpha Alumina                                         ______________________________________                                        19%       20.25%        60.75%                                                ______________________________________                                    

On an analysis basis, the catalyst composition was as follows:

    ______________________________________                                        NiO             CaO    Al.sub.2 O.sub.3                                       ______________________________________                                        19%             4%     77%                                                    ______________________________________                                    

EXAMPLE 3

This preparation has magnesium aluminate spinel as the support.Magnesium aluminate spinel has both chemical and physical propertieswhich are unique and result in a support having high thermal resistanceto the catalyst applied to the support migrating into the supportinterstitially. For these reasons it is also a highly satisfactorysupport.

The procedure for its preparation is as follows:

The following ingredients are carefully weighed out:

28.3 parts by weight of magnesite (M_(g) O).

63.7 parts by weight of alpha alumina having a surface area of 10 to 15m² /gm.

8.0 parts acid reactive alumina such as Boehmite (alpha aluminamonohydrate).

25.0 parts of recycle material.

Add all of the four ingredients to a muller and mill for about 10minutes.

2. Prepare a solution comprising 140 parts distilled or demineralizedwater and 17 parts 61% nitric acid. Stir to make uniform.

3. Add 32 parts by weight of the nitric acid solution of paragraph 2above to the milled powder.

4. Mix mull the resultant moist paste and then add about 6 parts byweight of distilled or demineralized water to the mixer and then mixmull for an additional 20 minutes.

5. Perform operations as set forth in paragraphs 5 through 7 of Example1.

6. Perform operations as specified in paragraphs 8 and 9 of the "SupportPreparation".

7. The shaped supports thus produced in the form of 7 spoked cylindersare "program fired" stepwise at temperatures of from 2200° F. to 2650°F. for a period of 4 hours in an oxidizing atmosphere.

8. The supports, again are impregnated as previously described byimmersion in a nickel nitrate solution, followed by drying andcalcination. This procedure is repeated until the nickel oxideconcentration of the finished catalyst is in the range of 19%. The finalcomposition of the catalyst after impregnation, drying and calcinationis as follows:

    ______________________________________                                        NiO            MgO     Al.sub.2 O.sub.3                                       ______________________________________                                        19%            22.9%   58.1%                                                  ______________________________________                                    

The magnesium oxide and the aluminum oxide constituents are present as amagnesium aluminate spinel. Alternately, the composition of this examplecan be spray dried with proper adjustment of the moisture content of themilled powder. Additionally, the shapes can also be varied as preferredfor the operation in which the support is to be used, and in the methodof forming of the structures; for example, by dry pressing, wet pressingor extruding.

EXAMPLE 4

The composition and procedure of this example produces a relatively highsurface area structure which has special desirable properties. Thecomposition includes rare earths and the method of developing thealumina gel structure is changed so that there are major differencesfrom the former examples. The preparative procedure is as follows:

1. Carefully weigh out the following ingredients:

2.1 parts of finely divided silica.

7.0±1 parts of mixed rare earths as their nitrates (mixed rare earthhave a nominal composition of 60% La₂ O₃, 15% CeO₂, 17.5% Nd₂ O₃ and7.0% Pr₈ O₁₁.

91.1 parts of Boehmite alumina such as Boehmite (alphamonohydrate).

Mill the three ingredients in a mix muller.

2. .[.weight.]. .Iadd.weight .Iaddend.out 75 parts of distilled ordemineralized water.

3. Add the distilled water of a paragraph 2 to the milled powder ofparagraph 1.

4. Perform operations as described in paragraph.Iadd.s .Iaddend.4, 5 and6 of "Support Preparation."

5. Blend the product of paragraph 6 in a blender in the ratio of 100parts powder to 3 parts of aluminum stearate and 1 part aluminum powder.

6. The instructions given in paragraphs 8 and 9 of "Support Preparation"are followed as given therein.

7. The supports in the form of 7 spoked cylinders from 9 are "programfired" stepwise through the range of from 250° to 1250° F. over 8hours.Iadd., .Iaddend.then are continued at 1250° F. for an additional 4hours making a total of 12 hours of calcining. The nitrate anion of therare earths is decomposed during this calcining. The firing is conductedin an oxidizing atmosphere. The shaped support structures are thenimmersed for multiple dips in a nickel nitrate solution as previouslyindicated. After dipping, drying and calcination, the final metalscontent of the catalysts is as follows:

    ______________________________________                                                                Silica Oxide                                          NiO   Rare Earth Oxide (ReO)                                                                          SiO        Al.sub.2 O.sub.3                           ______________________________________                                        19%   5.67%             1.7%       72.6%                                      ______________________________________                                    

EXAMPLE 5

A catalyst was prepared according to the procedure set forth in Example4, except that alpha alumina having a surface area in the range of 10 to15 m² /gm such as that used in Example 3 was substituted for theBoehmite (alpha monohydrate) such as that used in Example 4. Again, themixture of the rare earth metal nitrates of lanthanide series, such asthat used in Example 4 was mulled with the other constituents in thesame concentrations. As a result, the finished catalyst, after immersionin nickel nitrate solutions as previously indicated, had the samegeneral composition i.e.,

    ______________________________________                                        NiO    Rare Earth Oxides (Re)                                                                           SiO    Al.sub.2 O.sub.3                             ______________________________________                                        19%    5.67%              1.7%   72.6%                                        ______________________________________                                    

The difference in the two preparations was in the surface area of thefinished catalyst as is shown in Table III. The surface area for Example4 was 53.7 m² /gm whereas the surface area of the catalyst of Example 5was 11.5 m² /gm. After testing, the surface area of the catalyst ofExample 4 had been reduced somewhat to 47.52 m² /gm whereas the surfacearea of the catalyst in Example 5 actually showed an increase, (withinexperimental error) of 15.7%.

EXAMPLE 6

Another catalyst was prepared in accordance with the steps of Example 4,except that the rare earth metal nitrate solution was omitted from thepreparation. The finished catalyst contained

    ______________________________________                                        NiO             SiO    Al.sub.2 O.sub.3                                       ______________________________________                                        19%             1.7%   79.3%                                                  ______________________________________                                    

These catalysts, upon firing, shrank considerably since they were notstabilized by the rare earth oxides. Thus the particle .[.sizes.]..Iadd.size .Iaddend.of these catalysts was less than those of the otherexamples. Each of the catalysts were tested under identical conditions.200 cc of the catalyst pellets were placed in the reactor and naturalgas was fed over the catalyst at atmospheric pressure and at a dry gasfeed rate of 200 volumes of gas per volume of catalyst per hour. Thesteam to gas ratio was maintained at 3.0:1. Each of the catalysts weretested at temperatures of 1000°, 1200°, 1400° and 1600° F.

Essentially, all of the catalysts were identical or essentiallyidentical in nickel concentration. The carriers were of the same generalconfiguration except that the catalyst of Example 1B had a height of0.648 inches, versus the height of 0.293 inches for the remainingcatalyst. The equivalent hole diameter of each of the pie shaped gaspassages 9 expressed as a circle, .[.were.]. .Iadd.was .Iaddend.0.1372inches and therefore was identical for all samples. The only differencetherefore was in the height or the length of the tablet and the ratio ofH:ID. The longer of the samples i.e., the sample of Example 1B had aratio of 4.72:1, outside of the claimed range whereas the shorter of thesamples was within the claimed range of 2.14:1. The carrier compositionof Example 1A and 1B .[.were.]. .Iadd.was .Iaddend.identical. Some ofthe other samples varied. Thus, the carrier composition of Example 3 wasmagnesium aluminate. In Examples 4 and 5 the carrier composition wasstabilized by the addition of almost 6% of rare earth oxides of thelanthanide series. The results of the testing .[.is.]. .Iadd.are.Iaddend.shown in attached Table IV.

The activity can best be seen by noting the methane leakage at varioustemperatures. Looking, for example, at Examples 1A i.e., the shortercatalysts having the H:ID ratio in the claimed range versus Example 1Bhaving the H:ID ratio outside of the claimed range, the methane leakageat 1000° F. was 25.59 versus 41.5. At 1200° F. the methane leakage forthe catalyst 1A was 9.79 whereas the catalyst of Example 1B was at 21.Again, the superiority of the catalyst expressed as the lower methaneleakage became clear at temperatures of 1400° F. and 1600° F.respectively.

The amazing situation was that at 1000° F. the methane leakages ofExamples 2, 3, 4 and 5 were almost identical. The methane leakage ofExample 6.Iadd., .Iaddend.however, was slightly lower. Again, themethane leakage for Examples 2, 3, 4 and 5 were almost identical to themethane leakage for Example 1A, which was almost half of the methaneleakage of Example 1B. Again, the methane leakage of Example 6 appearedto be about half that of the other catalyst.

At 1400° F. the superiority of the catalyst supported on the variouscarriers was maintained so long as the H:ID ratio was within thepreferred range. Again, this was demonstrated at 1600° F. wherein themethane leakage for the seven spoked catalyst of different supportcomposition maintained a superiority so long as the H:ID ratio remainedthe same. It will be remembered however, that in the parent applicationsit was demonstrated that the Cordierite compositions i.e., Mg₂ Al₄ Si₅O₁₈ (magnesium alumino silicate) produced a less efficient catalyst forthis reaction. We have demonstrated however, in Table IV, that magnesiumaluminate produces good results and that alumina catalyst supports canbe promoted with rare earth oxides with good results. The surface areaof the catalyst prior to testing of Example 4 was 53.7 while the surfacearea of the catalyst prior to testing of Example 5 was 11.5 m² /gm. Thiswas due to the different aluminum oxide constituents utilized inpreparing the catalyst. After testing, the surface area of the testedcatalyst of Example 4 was still almost 50 m² /gm. The interesting pointis that the activities of each of these catalysts at 1000° F., at 1200°F., at 1400° F. and at 1600° F. were almost identical. It would havebeen predicted that the substantial difference in micro surface area ofcatalyst 4 would have produced a much more active catalyst. Such was notthe case. The failure of the catalyst to lose surface area under hightemperature conditions was due to the

                                      TABLE IV                                    __________________________________________________________________________                                Example 2   Example 4                                                                           Example 5                                                   7 spoked                                                                            Example 3                                                                           7 spoked                                                                            7 spoked                                                    wheels                                                                              7 spoked                                                                            wheels                                                                              wheels                                                                              Example 6                                Example 1A & 1B                                                                            OD .648"                                                                            wheels                                                                              OD .648"                                                                            OD .648"                                                                            7 spoked                                 7 spoked wheels                                                                            Ht. .293"                                                                           OD .648"                                                                            Ht. .293"                                                                           Ht. .293"                                                                           wheels                                   OD .648"     Alumina/                                                                            Ht. .293"                                                                           Alumina                                                                             Alumina                                                                             OD .648"                                 1A     1B    Calcium                                                                             Magnesium                                                                           Rare Earth                                                                          Rare Earth                                                                          Ht. .293"                                Ht. .293"                                                                            Ht. .648"                                                                           Oxide Aluminate                                                                           Oxide Oxide Alumina                                  H:ID 2.14                                                                            H:ID 4.72                                                                           H:ID 2.14                                                                           H:ID 2.14                                                                           H:ID 2.14                                                                           H:ID 2.14                                                                           H:ID                      __________________________________________________________________________                                                        2.14                      Crush lbs./DWL                                                                Carrier        59     120   40    48    34    45    37                        Dipped         66     116   49    75.5  51    66    64.5                      Density (CBD)                                                                 Carrier, #/CF  52.1   --    32.0  41.0  39.6  51.1  47.9                      Dipped, #/CF          --    54.9  53.8  52.3  63.9  60.8                      H.sub.2 O Pickup                                                              Carrier, %     21.0   --    39.0  29.7  33.4  25.4  27.0                      Surface Area                                                                  Carrier, m.sup.2 /g                                                                          1.64   2.37  6.60  2.35  22.6  1.38  1.57                      Catalyst, m.sup.2 /g                                                                         2.71   2.3   24.6  9.4   53.7  11.5  14.1                      Pore Volume > (350 Å)                                                     Carrier, cc/g  0.22   0.23  0.47  0.32  0.34  0.25  0.29                      Catalyst, cc/g 0.16   0.16  0.38  0.25  0.23  0.17  0.19                      NiO Crystallite Size, Å                                                                  250    325   400   150   150   210   210                       % CH.sub.4 Leakage 1600° F.                                                           1.14   5.10  1.13  0.67  0.75  0.96  0.17                      1400° F.                                                                              4.48   12.4  3.07  1.90  2.18  2.20  0.91                      1200° F.                                                                              9.79   21.0  10.78 8.98  9.37  9.11  5.25                      1000° F.                                                                              25.59  41.5  26.90 24.62 25.5  24.56 18.94                     Properties After Activity Test                                                Crush (Reduced) lbs/DWL                                                                      82     116   52    81.0  83.0  49.5  40.5                      % C            0.08   0.139 0.116 0.097 0.080 0.163 0.181                     Surface Area, m.sup.2 /g                                                                     1.3    2.4   2.0   3.2   47.5  15.7  12.3                      Pore Volume > (350 Å) cc/g                                                               0.15   0.16  0.15  0.23  0.20  0.37  0.23                      Ni Crystallite Size (Å)                                                                  140    290   325   210   200   --    165                       Activity Test Conditions                                                      Catalyst Volume (cc):                                                                        200                                                            Feedstock:     Natural Gas                                                    Pressure:      Atmospheric                                                    Dry Gas Feed Rate (1/hr.)                                                                    200                                                            Steam/Gas Ratio:                                                                             3.0/1                                                          __________________________________________________________________________     *"% Methane Leakage" is a term of convenience. The lower the leakage the      more complete is the reaction. Thus a low "methane leakage" is an             indication of high activity.   stabilizing effect of the rare earth oxide     promoter. Since the beginning preparation of Example 5, had a low surface     area, such advantage was not achieved. However, insofar as activity was     concerned there appeared to be no essential difference. This demonstrates     therefore that this invention requires a cylindrical refractory support     having two or more gas passages extending axially therethrough and having     a catalytically active amount of group VIII metal oxide deposited thereon.     Specifically, we have found that the catalyst should have a Relative     Activity Coefficient Factor (AC.[.R.]..Iadd.F.[.®.]..Iadd..sup.R     .Iaddend.),(as defined herein) and a Relative Pressure Factor     (PF.[.®.]..Iadd..sup.R .Iaddend.) (as defined herein), in excess of     that of a standard ring, and the     .Iadd.(.Iaddend.ACF.[.®.]..Iadd..sup.R) .Iaddend.should be in excess     of .[.1.]. .Iadd.1.15 .Iaddend.the ratio of     .Iadd.(.Iaddend.ACF.[.®.]..Iadd..sup.R) .Iaddend.to PF.[.®.].     .Iadd..sup.R .Iaddend.should be in excess of .[.1.]..Iadd.1.125.Iaddend..     Further, we have found tht the height (H) of the catalyst support should     bear a relationship to the effective internal diameter (ID) of each of     said gas passages of said support. Therefore, the ratio of H:ID of said     catalyst support should be less than 4:1. This critical ratio has been     experimentally demonstrated in both bench and pilot scale studies.

The geometric or macro surface area, as demonstrated in these examplesand particularly the effective surface area of the walls of the interiorgas passages 9 as shown herein do have a substantial effect on theactivity of the reaction. Thus, as is shown, there is a substantialdifference in activity between Examples 1A and 1B. This is also truewhen the catalyst of Example 1B is compared with the catalysts ofExamples 2 through 6.

It is felt therefore, that the specific height to effective internaldiameter of ratio (H:ID) for multiholed catalysts when used inendothermic reactions of this type is of relatively wide spreadapplication, and the geometric features of this invention are applicableto a wide variety of refractory supports. The metal aluminate spinelsoffer excellent supports so long as the metal forming the spinel doesnot migrate under reaction conditions or at reaction temperatures.

Many modifications will occur to those persons skilled in the art fromthe detailed description presented herein, which was meant to beexemplary in nature and nonlimiting, except so as to be commensurate inscope with the scope of the appended claims.

We claim:
 1. A .[.hydrocarbon reforming.]. catalyst, comprising a.[.cylindrical.]. .Iadd.cylindrical .Iaddend.refractory support.[.selected from the group consisting of aluminum oxide, magnesiumoxide, calcium oxide and metal aluminate spinels, and.]. having two ormore gas passages extending axially therethrough from one end to theother and a catalytically-active metal comprising nickel or cobalt oxidedeposited thereon .[.in a concentration of 6% to 30% by weight,expressed as the metal oxide.]., said catalyst having a RelativeActivity Coefficient Factor (ACF.[.®.]..Iadd.^(R) .Iaddend.) and aRelative Pressure Factor (PF.[.®.]..Iadd.^(R) .Iaddend.) being in excessof that when compared to a standard ring, said ACF.[.®.]..Iadd.^(R).Iaddend.being in excess of .[.1.]. .Iadd.1.15 .Iaddend.and the ratio ofACF.[.®.]..Iadd.^(R) .Iaddend.to said PF.[.®.]..Iadd..sup. R.Iaddend.being in excess of .[.1:1.]. .Iadd.1.25:1, .Iaddend.the Height(H) of said support bearing a relationship to the effective internaldiameter of each of said gas passages (ID), the ratio of H:ID being lessthan 4:1.
 2. A .[.hydrocarbon reforming.]. catalyst, as defined in claim1, in which said .[.cylindrical.]. .Iadd.cylindrical .Iaddend.refractorysupport is in the form of a spoked wheel, having a peripheral rim, acentrally-located hub and a plurality of radially-extending spokes,defining pie-shaped gas passages.
 3. A .[.hydrocarbon reforming.].catalyst, as defined in claim 1, in which said support has a surfacearea in the range of from 0.5 to 55 m² /gm. .Iadd.4. A catalyst, asdefined in claim 1, in which said catalytically-active metal is nickeloxide..Iaddend. .Iadd.5. A catalyst, as defined in claim 1, in whichsaid catalytically-active metal is cobalt oxide..Iaddend. .Iadd.6. Acatalyst, as defined in claim 1, in which said catalytically-activemetal is present in a concentration of from 6% to 30% by weight,expressed as the metal oxide..Iaddend. .Iadd.7. The catalyst, as definedin claim 1, in which said refractory support consists essentially ofaluminum oxide..Iaddend.